Algebra universalis

, Volume 73, Issue 3–4, pp 391–417 | Cite as

Commutative idempotent groupoids and the constraint satisfaction problem

  • Clifford Bergman
  • David Failing


A restatement of the Algebraic Dichotomy Conjecture, due to Maroti and McKenzie, postulates that if a finite algebra A possesses a weak near-unanimity term, then the corresponding constraint satisfaction problem is tractable. A binary operation is weak near-unanimity if and only if it is both commutative and idempotent. Thus if the dichotomy conjecture is true, any finite commutative, idempotent groupoid (CI groupoid) will be tractable. It is known that every semilattice (i.e., an associative CI groupoid) is tractable. A groupoid identity is of Bol–Moufang type if the same three variables appear on either side, one of the variables is repeated, the remaining two variables appear once, and the variables appear in the same order on either side (for example, \({x(x(yz)) \approx (x(xy))z}\)). These identities can be thought of as generalizations of associativity. We show that there are exactly 8 varieties of CI groupoids defined by a single additional identity of Bol–Moufang type, derive some of their important structural properties, and use that structure theory to show that 7 of the varieties are tractable. We also characterize the finite members of the variety of CI groupoids satisfying the self-distributive law \({x(yz) \approx (xy)(xz)}\), and show that they are tractable.

Key words and phrases

constraint satisfaction CSP dichotomy Bol–Moufang Plonka sum self-distributive squag quasigroup prover9 mace4 uacalc 

2010 Mathematics Subject Classification

Primary: 08A70 Secondary: 68Q25 08B25 


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Copyright information

© Springer Basel 2015

Authors and Affiliations

  1. 1.Department of MathematicsIowa State UniversityAmesUSA
  2. 2.Department of MathematicsQuincy UniversityQuincyUSA

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